Within the meaning of the present invention, "patterning" is to be considered primarily as colored patterning, in which context one should think not only of a true illustration or pattern, but of solid-shade dyeing as well. The active manner in which the patterning on the web is accomplished is not important for the present invention. In many cases, it will be a printing process, but patterning processes that also come into consideration are a dropping, pouring or spraying of the pattern on the web, or even where the web is dipped into a patterning liquor.
The present invention concerns patterning processes of this type, where a thickening agent must be present on the web. This is primarily the case with printing processes to prevent the patterning agent from running, thus forming a clean contour, or to prevent the patterning agent from penetrating too quickly into the depth of the textile material. The use of thickening agents in textile printing is described in the book "Fundamentals of Textile Finishing" by M. Peter and H. K. Rouette, 13th edition (1989), pages 620 to 623, and a number of suitable substances are enumerated. Of course, mixtures of several suitable substances must also be regarded as thickening agents.
In the case of printing, the thickening agent is in the applied medium, i.e., the printing paste. This also holds true when a thickening agent must be used in carpet dyeing to prevent the applied patterning agent from sinking too quickly into the pile, which in the case of carpets is quite high, thus assuring that the tips of the fibers receive enough dye, so that a frosting effect does not develop. The thickening agent added to the dyeing liquor in these cases also keeps the liquor on the top areas of the fibers for a sufficient time.
However, there are also cases when thickening agent is not applied together with the patterning agent, but is applied beforehand. An example for this can be gathered from the German Patent No. 27 08 000 A1, in which the thickening agent (gum) is used as a dye retardant and is applied in a coating on a carpet web, upon which a non-repeating pattern is subsequently dropped using dyeing liquors. However, even here, when the patterning is completed and the goods are in the steamer, thickening agents are present.
These thickening agents must be removed again from the web after the steaming process. This is a difficult task and requires considerable expenditure for washing. Many attempts have been made to facilitate the removal of the thickening agent. For example, the thickener has first been moistened, whereupon it has passed through a soaking section in order to let the thickener swell due to the moisture. After that, it is supposed to be easier to wash out.
Until now, the washing expenditure to remove the thickener was always considerably greater than in the normal dyeing process where no thickening agents are necessary.
At the end of the steamer, the thickening agents form a true layer on the web. It has already been undertaken to mechanically remove this layer in the end region of the steamer by doctoring, so that at least a substantial portion of the thickening agent was already removed from the web without a washing process, thus the washing process was relieved accordingly (as shown in German laid open print No. 34 40 948).
However, all these known measures were from the aspect of merely removing the thickening agent, which subsequently had to be disposed of in a costly manner.